Enable chrome_public_test_apk on android-marshmallow-arm64-rel

Bug: 731759
Change-Id: Ic05571ebffa95bf08bae2b16be846d934e8cc7ae
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1807778Reviewed-by: John Budorick <jbudorick@chromium.org>
Commit-Queue: Yun Liu <yliuyliu@google.com>
Cr-Commit-Position: refs/heads/master@{#697001}

testing/buildbot/chromium.android.json

@@ -26292,7 +26292,6 @@
           "--gs-results-bucket=chromium-result-details",
           "--recover-devices"
         ],
-        "experiment_percentage": 100,
         "merge": {
           "args": [
             "--bucket",

testing/buildbot/test_suite_exceptions.pyl

@@ -301,11 +301,6 @@
           'shards': 12,
         },
       },
-      'android-marshmallow-arm64-rel': {
-        # TODO(crbug.com/731759): Enable this once we're confident that it
-        # passes.
-        'experiment_percentage': 100,
-      },
       'KitKat Phone Tester (dbg)': {
         'swarming': {
           'shards': 20,